An optical spectrometer (also referred to as a spectrometer) is an instrument used to measure properties of light over a specific portion of the electromagnetic spectrum. The variable measured is the light's intensity for each light frequency. Spectrometers were developed in early studies of physics, astronomy, and chemistry. The capability of spectroscopy to determine chemical composition drove its advancement and continues to be one of its primary uses. Spectrometers are used in astronomy to analyze the chemical composition of stars and planets.
A spectrometer often comprises an optical system and optical detectors. The optical system causes optical dispersion of the light by, e.g., refraction using a prism, or by diffraction using a diffraction grating. The optical detectors detect different components of the dispersed light with different frequencies. For example, in a spectrometer using prism, a slit selects a thin strip of light which passes through the collimator and gets parallelized. The parallelized light then passes through the prism, in which it is refracted twice (once when entering and once when leaving). Due to the nature of the dispersive element, the angle with which light is refracted depends on its wavelength. This leads to a spectrum of thin lines of light, which may be detected by the optical detectors. Replacing the prism with a diffraction grating result in a grating spectrometer.
Recently, there has been a growing interest in developing miniaturized spectrometers that may be integrated into or with semiconductor devices for use in digital mobile devices, such as smart phones, tablets, or the like. New applications enabled by the miniaturized spectrometers integrated in digital mobile devices may encompass many aspects of everyday life, such as assessing the quality of food, material analysis for detecting counterfeit products, fitness and health detection, or telemedicine.